1.Field of the Invention
The present invention relates to a linear guide apparatus used with an industrial machine such as a machine tool, robot and the like. More particularly, it relates to a linear guide apparatus in which a coating layer is formed on a slider body.
2.Related Background Art
As shown in FIGS. 5 and 6, in a typical conventional linear guide apparatus, axial rolling member receiving grooves 3 are formed in both longitudinal side surfaces of a guide rail 1 which extends axially and on which a slider 2 is mounted for axial relative movement with respect to the guide rail. The slider 2 comprises a metallic (e.g. copper) slider body 2A and a pair of plastic end caps 2B. Load rolling movement grooves 5 which are opposed to the rolling member receiving grooves 3 are formed in inner surfaces of the slider body 2A and rolling member returning passages 7 comprising through holes parallel with the grooves 3 are formed in skirt portions of the slider body. Each end cap 2B is provided with an arcuate passage 8 connecting the respective rolling movement groove 5 and the respective returning passage 7 and is secured to a corresponding end surface of the slider body 2A by screws n.
A number of rolling members (for example, steel balls) 6 are filled in a corresponding rolling member circulating path constituted by the respective rolling movement groove 5, rolling member returning passage 7 and arcuate passage 8, and these rolling members are held by a holder H in such a manner that, even when the slider 2 is dismounted from the guide rail 1, the rolling members do not come out from the rolling movement groove 5.
The linear guide apparatus having the above-mentioned arrangement is used, for example, to linearly guide a moving member of an industrial machine by attaching the guide rail 1 to a fixed surface of the industrial machine and attaching the slider 2 to the moving member of the industrial machine. When the slider is shifted together with the moving member of the industrial machine, the number of rolling members 6 inserted between the respective rolling member receiving grooves 3 of the guide rail 1 and the respective rolling movement grooves 5 of the slider 2 are shifted toward the end of the slider 2 at a speed slower than a moving speed of the slider 2 while supporting the load. When each rolling member reaches the end of the slider, it is turned back along the arcuate passage 8, and then is shifted through the returning passage 7 to reach the other arcuate passage 8 formed in the other end of the slider 2, where each rolling member is returned to the rolling movement groove 5 again.
Lubricant such as lubricant oil or grease poured from an oil supply nipple g is supplied to the rolling movement groove 5, rolling members 6 and rolling member receiving groove 3, thereby ensuring the smooth movement of the slider 2.
When the linear guide apparatus attached to the linearly moving portion of the industrial machine is being used, dust is accumulated in the exposed areas of the rolling member receiving grooves 3 of the guide rail 1 and the like and enters into the interior of the slider 2, thereby adding resistance to the rolling movements of the rolling members 6. To avoid this, normally, a dust preventing side seal 10 is attached to each end cap 2B. Further, an under seal (not shown) is attached to an under surface of the slider 2 to prevent the dust from entering into the interior of the slider from a lower portion of the slider.
In the above-mentioned conventional linear guide apparatus, the copper slider body 2A of the slider 2 must be machined by effecting machining operations such as cutting grinding and threading to form the rolling movement grooves 5 within which the rolling members 6 are rolled, the returning passages (through bores) 7 for circulating the rolling members 6 and the like. The accuracy of such machining operations greatly influences the accuracy of the linear guiding movement. However, normally, the slider body 2A is not subjected to any surface treatment and lubricant is merely coated on the slider body to prevent the body from rusting. Thus, although the surfaces of the rolling movement grooves 5 and the returning passages 7 to which the lubricant is always supplied are not easily rusted, there is a risk that the other portions of the slider body on which the lubricant was initially coated will become rusted after a long time has elapsed, thereby degrading the interior of the machine. Further, to prevent rusting in the forwarding of the apparatus, the apparatus must be coated by the anti-rust lubricant and then be rigorously packed to prevent the rust, thereby increasing the labor and cost.
In order to eliminate the aforementioned drawbacks, as disclosed in the Japanese Patent Publication No. 2-55515, there has been proposed a technique in which plating layers are formed on all of the outer surfaces of the slider body, other than the attachment reference surface and the load transferring surfaces, by black chrome plating treatment. The black chrome plating treatment is advantageous in that the slider body is hard to be rusted and the rust is unobtrusive accompanying effects cannot be expected at all. However, in such linear guide apparatuses, since the lubricant is always supplied to the relative rolling movement portions, it is necessary to prevent the leakage of the lubricant in order to ensure the smooth movements of the rolling members. Further, since a plurality of screws are threaded in the slider body, it is required to prevent the screws from unthreading.